Wood rot

If you have the skills, time, work space and help available you can probably fix up the old rig well enough to be somewhat comfortable and safe to drive. Critical safety items include tires, (if over six years old by date codes, may be ready to blow), brakes (including changing brake fluid and replacing old flexible front brake lines), engine cooling system (including radiator, clutch fan, water pump and all belts and hoses) propane system and propane leak alarm. A working dash AC unit is important on hot days and to cope with engine heat. Your 12 volt interior lights, appliance controls, furnace and fridge all depend on your "house" batters and converter/charger working properly as well as relay that provides charging current to the house batteries while driving. Keep in mind that whatever you invest in time, your owm labor or paid for labor, plus replacements, parts and materials, your rig may have a market value of less than $4000. You may be better off selling the rig for whatever it will bring.
An old RV is like an old cabin cruiser boat, a potential money pit.